1. Field of the Invention
This invention relates to a continuously variable transmission for motor vehicles which is capable of shifting and transmitting power from a driving member to a driven member by moving a carrier carrying a shifting rotating member in friction contact with the driving and driven members.
2. Description of Background Art
A continuously variable transmission for motor vehicles is disclosed in Japanese Patent Laid-Open No. Hei 10-184841.
A motor vehicle such as a motorcycle mounted with this type of continuously variable transmission, when pushed to move, is required to be moved with a small force without the necessity of a great force for overcoming a frictional force on each part of the continuously variable transmission. In a conventional continuously variable transmission, a neutral clutch for the connection and disconnection of a power transmission is provided between an output gear in mesh with the driven member and an output shaft connected with a driving wheel. That is, it is necessary to provide a power transmission and interruption means between the continuously variable transmission and the driving wheel separately from the continuously variable transmission. Therefore, this type of transmission increases the number of components and accordingly resulting in an increased in the cost.
In view of the above-described problem inherent in the heretofore known art, it is an object of this invention to provide a continuously variable transmission for motor vehicles which requires no other mechanism than the continuously variable transmission and allows an easy movement of the motor vehicle by pushing with a small force.
To accomplish the above object, the continuously variable transmission for motor vehicles of a first embodiment of the invention comprises a transmission shaft rotated by power from an engine, a driving member rotated together with the transmission shaft, a driven member rotatably supported on the transmission shaft, a carrier movable along the axis of the transmission shaft, a support shaft which has an axis along a conical generator having its centerline on the axis of the transmission shaft and is supported on the carrier, and a shifting rotating member having conical first and second friction transfer surfaces which are in respectively frictional contact with the driving member and driven member, rotatably and axially slidably supported on the support shaft. The continuously variable transmission is characterized by including a power disconnecting means which is capable of releasing at least one of the driving member and the driven member from friction contact with the first and second friction transfer surfaces by driving at least one of the driving member and the driven member so that the rotating members will move away from each other along the axis of the transmission shaft.
According to the above-described constitution, power transmission to the continuously variable transmission can be interrupted by releasing at least either one of the friction contact of the driving member with the first friction transfer surface and the friction contact of the driven member with the second friction transfer surface by the power disconnecting means, thereby enabling the light movement of the motor vehicle such as a motorcycle simply by pushing with a slight force. Besides, the power disconnecting means drives at least one of the driving member and the driven member which make up the continuously variable transmission, along the axis of the transmission shaft. It is, therefore, possible to decrease the number of components and lower the cost as compared with a conventional transmission which needs the neutral clutch which is a mechanism separate from the continuously variable transmission.
In a second embodiment of the invention, in addition to the constitution of the first embodiment, the power disconnecting means is characterized in that, with the movement of the carrier from the position of LOW gear ratio to the side opposite to TOP gear ratio, at least either one of the driving member and the driven member is driven to move in the axial direction of the transmission shaft. According to the above-described constitution, power transmission can be interrupted by the use of a continuously variable transmission of a simple structure in the position of the carrier, and therefore, no other special power is needed for operating the power disconnecting means than the driving source for driving the carrier. Besides, the NEUTRAL state for interruption of the power transmission from the engine to the driving wheel is achieved in accordance with the movement of the carrier from the position of LOW gear ratio to the opposite side of TOP gear ratio. It is, therefore, possible to simplify the structure for changing from the position of LOW gear ratio to NEUTRAL position.
In a third embodiment of the invention, in addition to the constitution of the second embodiment, the continuously variable transmission is characterized in that the driven member is rotatably supported on the transmission shaft and movable within a limited range in the axial direction of the transmission shaft, and is urged with a spring into friction contact with the second friction transfer surface. A thrust bearing which is the power disconnecting means is mounted in the inner peripheral section of the carrier, to thereby enable pushing of the driven member in the axial direction of the transmission shaft with the movement of the carrier from the position of LOW gear ratio to the opposite side of TOP gear ratio. According to such a constitution, the driven member can be driven towards the direction away from the driving member while restricting the occurrence of a frictional force between the driven member and the carrier. Besides, because of a slow peripheral speed on the inner periphery of the carrier, it is possible to reduce the load acting on the thrust bearing.
Furthermore, a fourth embodiment of the invention, in addition to the constitution of the first embodiment, a pressure control cam mechanism is provided between the first rotating member which is at least one of the driving member and the driven member, and the second rotating member rotatable around the axis of the transmission shaft without changing its position along the axis of the transmission shaft. The pressure control cam mechanism transmits the power between the first and second rotating members while producing a surface pressure for pressing the driving member and the driven member against the first and second friction transfer surfaces. The movement of the first rotating member toward the position for releasing at least one of the driving member and the driven member from friction contact with the first and second friction transfer surfaces is absorbed by the pressure control cam mechanism. According to this constitution, at least one of the driving member and the driven member is allowed to move in the axial direction during power interruption while securing friction contact during power transmission between the driving and driven members and the first and second friction transfer surfaces.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.